Saved from extinction, southern California’s Channel Island foxes now face a new threat to survival

Beginning in the 1990s, Island Fox populations began to decline due to an outbreak of canine distemper and an increase in golden eagle attacks. Some islands saw their population drop to as few as 15 individuals, but federal government conservation efforts restored the numbers for 2017.

A new study by USC’s Dornsife College of Letters, Arts and Sciences reveals a troubling decline in genetic diversity within the species, indicating a new threat to the survival of Channel Island foxes. Declining genetic diversity reduces the ability of foxes to adapt to future challenges such as climate change and introduced pathogens, putting their survival at risk once again. Although foxes have low genetic diversity, they do possess diverse gut microbiomes that could help them cope with environmental changes.

The tiny foxes, each no bigger than a five-pound house cat, that inhabit the Channel Islands off the coast of southern California were saved from extinction in 2016. However, new research reveals that foxes are now they face a different threat to their survival.

Suzanne Edmands, a professor of biological sciences in the USC Dornsife College of Letters, Arts and Sciences, and Nicole Adams, who earned her PhD from USC Dornsife in 2019, found that the genetic diversity of foxes has decreased over time, which possibly endangers their survival and the biodiversity of the islands.

“The findings of this study highlight the alarming fact that foxes currently inhabiting six of the Channel Islands possess extremely low genetic diversity, potentially making them more susceptible to hazards such as disease outbreaks and climate-induced environmental changes. weather,” Edmands said.

As the largest land animals native to islands located 22 miles off the coast of southern California, these big-eared, bushy-tailed creatures play a vital role in regulating plant and animal communities by consuming diverse food sources. , which include fruits, insects, snails. , lizards, birds and rodents. In fact, many plant species depend on them to distribute seeds through their droppings.

“The importance of these animals to the overall biodiversity of the island cannot be overstated. Without them, we could lose other species as well,” Edmands said.

A previous study conducted in 2018 lacked sufficient samples to detect changes in genetic variation. This new study used a broader sampling method, comparing historic museum specimens and modern blood samples.

Bushy-tailed and large-eared, Channel Island foxes play a vital role in regulating plant and animal communities. (Photo: by Karl Huggins.)

Interestingly, the results indicated extremely low genetic variation even before the population declined. It also revealed that genetic variation had shrunk further since the population fell. The islands that experienced the most severe losses, San Miguel and Santa Rosa, also showed the greatest reduction in genetic diversity. Santa Cruz and Santa Catalina, two islands where populations fell moderately, showed mixed changes in genetic diversity metrics.

Placing these island foxes on the endangered species list between 2004 and 2016 played a crucial role in the population’s recovery. By 2017, a year after they were removed as an endangered species, the Catalina population was found to have increased over that 13-year period from about 100 to over 2,000, while the Santa Island fox population Rosa rose from a low of 15 to over 1,200 during the same time frame. However, their depleted genetic diversity continues to hamper the foxes’ ability to adapt to future challenges such as global warming and introduced diseases.

While genetic variation is crucial for resistance to disease and adaptation to climate change, the scientists found a silver lining to their research. They found reasonably good diversity within the fox gut microbiome, a key player in boosting immunity and general well-being.

“This discovery suggests that foxes may have evolved an alternative mechanism to cope with changing environmental conditions,” Edmands said.

The study also reveals greater divergence between the six islands over time. This finding complicates the potential conservation strategy of moving foxes between islands to increase genetic variation. Such a move could inadvertently disrupt local adaptation by producing offspring less fit or not as well adapted to their specific environments. It should be noted that each island population is recognized as a separate unique or endemic subspecies.

Given their limited ability to respond to new challenges, long-term monitoring of the fox population is crucial. To that end, the researchers have already begun non-invasive monitoring by sequencing bacterial communities in the foxes’ scat.

“The recovery of the fox population is an incredible conservation success, but its fragile genetic condition means that continued monitoring is critical to ensure its survival,” Edmands said.